Chronic rhinosinusitis (CRS) is a common condition defined by symptomatic inflammation of the paranasal sinuses lasting longer than 12 weeks. Up to 16% of the population is affected by this condition. Cavities associated with CRS include the maxillary, frontal, ethmoid, ostiomeatal complex, ethmoid infundibulum and sphenoid sinuses as well as the middle meatus location, or a combination thereof. Common symptoms of CRS include impaired nasal obstruction, facial pressure or fullness, nasal discharge, and olfactory loss; these symptoms likely arise due to mucosal inflammation, local infection, and/or impairment of mucociliary function.
While there is no approved therapy for the treatment of CRS, evidence-based medical management supports the use of a host of oral or topical corticosteroid therapies for the disease. High-volume, daily saline irrigation with adjunct application of a topical corticosteroid via nasal sprays is common as a first-line therapy. Second line agents for flare-ups and worsening disease include a short course of oral corticosteroids, although this approach can lead to unintended systemic side effects including glaucoma, osteoporosis and avascular necrosis of the hip and shoulder. It is estimated that up to 12-50% of CRS patients do not respond positively to this recommended medical regimen and are often candidates for Functional Endoscopic Sinus Surgery (FESS) and/or balloon sinuplasty dilation.
Avoidance of surgical interventions in the treatment of CRS would be ideal for patients since these procedures carry surgery-associated risks, cause post-operative pain and discomfort, and require burdensome and costly post-operative cleaning. Clinical data has demonstrated that topical corticosteroids are effective in reducing inflammation associated with CRS and thus, are a rational choice for the management of this condition.
An ideal treatment for CRS would provide local and sustained anti-inflammatory drug delivery in the sinuses of patients as an alternative treatment option to sinus surgery. Such a therapy would ideally establish safe and effective sustained drug delivery localized to the inflamed tissue and in some cases could prevent the need for surgery.
FESS involves removal of bone and tissue to enlarge sinus outflow tracts, widen sinus openings or ostia and allow for ventilation of previously obstructed sinus cavities and restoration of mucociliary clearance. Currently, there are approximately 500,000 procedures performed annually in the United States.
By removing small pieces of bone, polyps, and/or debridement of tissue within the sinus cavities, FESS has proven to be an effective way to improve the drainage pathway of the sinuses. However, a significant number of postoperative complications such as inflammation, swelling, disease recurrence, need for repeat procedures and synechiae are often observed. Postoperative care is therefore an important component of FESS. Approximately 10-20% of FESS patients become refractory, do not respond to treatment, and may require additional surgical intervention or lifelong medical therapy.
Some form of sinus packing is generally conducted postoperatively to FESS. Examples of packing materials include simple dressings moistened with saline, foam dressings based on polysaccharide gel, PEG-based materials, and middle meatal spacers. Implantable sinus stents have also been devised and these scaffolds are intended to stabilize the sinus openings and the turbinates, reduce edema, and/or prevent obstruction by tissue adhesion. They also have the capability of being integrated with therapeutic agent(s) that may be delivered topically over time. This local delivery of therapeutic agent(s) may be superior to topical application in the postoperative setting. In this regard, the USFDA-approved PROPEL™ system (Intersect ENT, Menlo Park, Calif., USA) is a self-expanding, bioresorbable, steroid-eluting stent that is intended for use in the ethmoid sinus post-FESS.